This program project consists of a collaborative study of the cellular and molecular aspects of the transport of respiratory gas between the ambient air and the sub-cellular site of metabolism. The constituent research projects can be subdivided into: 1. Pulmonary cellular function including lipid metabolism of the lung, particularly of the type II cells, which cells will be studied in tissue culture both as a means of obtaining pure suspensions and for intrinsic characterization, and including broad studies on the physiology of the smooth muscle of the airways. 2. Blood as a transport tissue including rapid chemical reactions of whole blood and hemoglobin, and red cell exchanges, of respiratory gases and CO, as well as the intracellular activity of carbonic anhydrase and the speed of acid-base readjustments of blood in the living animal. 3. Transport of respiratory gases in tissues including several unique techniques of estimating tissue PO2 such as mitochondrial oxygen consumption in state III, 18O indicator dilution and CO-O2 myoglobin equilibrium, as well as the control of vascular smooth muscle by PO2 and the effect of pulsatility on capillary exchanges. There are in addition three Core Facilities; A. A mass spectrometer facility with 2 instruments for the measurement of stable isotopes, B. A spectro fluoremetric analytical facility for the measurement of intracellular metabolite concentrations, C. Administrative facility for the entire program. The program consists primarily of the respiratory group of the Department of Physiology, which operates a training program in respiratory physiology, and will be closely correlated with other investigations in the pulmonary area such as the SCOR and investigators in clinical departments.